Lung cancer is one of the most common cancers in industrial nations and has an extremely high mortality rate. Early diagnosis and effective treatments are not available at this time. A chest X-ray is frequently used for lung cancer screening, however, it is not useful for the detection of early stage cancer. CT scans may also be used and may allow detection of the cancer at an earlier stage, however, this procedure takes time and has a risk of exposure.
Cancer cells or micrometastases are frequently detected in the blood stream of patients with melanomas, thyroid cancers, and prostate cancers. Currently reverse transcription-based polymerase chain reaction (RT-PCR) is a powerful method capable of detecting a single cancer cell within millions of normal blood cells by amplifying a cancer specific gene or marker. This makes RT-PCR detection of micrometastases a promising diagnostic procedure for the prognosis, choice of appropriate treatments, and monitoring of the efficacy of each treatment. Furthermore, blood tests do not induce any health hazards, whereas methods such as X-ray or CT scan do. In addition, blood tests cause very minor physical discomfort as compared to endoscopic examination and biopsy. Lung cancer frequently induces blood-born metastasis even in the early stages—before symptomatic disease and many lung cancers relapse as distant metastases, such as in brain, bone, and liver. This is due to the lung cancer induced blood-borne metastasis. This knowledge can be used, however, because it suggests that the diagnosis and detection of relapse could be made on the basis of these blood borne metastases at a very early stage. However, there are no good markers available for the identification of the metastatic lung cancers cells in the blood. Currently, lung cancer markers such as cytokeratin-19 and CEA are used for the diagnosis of non-small cell lung cancer by RT-PCR (reverse transcriptase polymerase chain reaction) but lack specificity, and result in a high number of false positives and negatives.
RT-PCR of micrometastases, then, is especially advantageous for the detection of lung cancer due to the large patient population, high incidence of blood-borne metastasis, poor prognosis, and high medical cost for advanced cancer treatments. In addition, specific antibodies are not available as of yet for lung cancer.
Therefore, specific markers and a method of diagnosis of lung cancer by detecting blood-borne metastasis is needed.